Hydrocarbon production from subterranean formations commonly includes a wellbore completed in either cased hole or open hole condition. In cased-hole applications, a wellbore casing is placed in the wellbore and the annulus between the casing and the wellbore is filled with cement. Perforations are made through the casing and the cement into the production zones to allow formation fluids (such as, hydrocarbons) to flow from the production zones into the casing. A production string is then placed inside the casing, creating an annulus between the casing and the production string. Formation fluids flow into the annulus and then into the production string to the surface through tubing associated with the production string. In open-hole applications, the production string is directly placed inside the wellbore without casing or cement. Formation fluids flow into the annulus between the formation and the production string and then into production string to surface.
When producing fluids from subterranean formations, especially poorly consolidated formations or formations weakened by increasing downhole stress due to wellbore excavation and fluids withdrawal, it is possible to produce solid material (for example, sand) along with the formation fluids. This solids production may reduce well productivity, damage subsurface equipment, and add handling cost on the surface. Several downhole solid, particularly sand, control methods being practiced in industry are shown in FIGS. 1(a), 1(b), 1(c) and 1(d). In FIG. 1(a), the production string or pipe (not shown) typically includes a sand screen or sand control device 1 around its outer periphery, which is placed adjacent to each production zone. The sand screen prevents the flow of sand from the production zone 2 into the production string (not shown) inside the sand screen 1. Slotted or perforated liners can also be utilized as sand screens or sand control devices. FIG. 1(a) is an example of a screen-only completion with no gravel pack present.
One of the most commonly used techniques for controlling sand production is gravel packing in which sand or other particulate matter is deposited around the production string or well screen to create a downhole filter. FIGS. 1(b) and 1(c) are examples of cased-hole and open-hole gravel packs, respectively. FIG. 1(b) illustrates the gravel pack 3 outside the screen 1, the wellbore casing 5 surrounding the gravel pack 3, and cement 8 around the wellbore casing 5. Typically, perforations 7 are shot through the wellbore casing 5 and cement 8 into the production zone 2 of the subterranean formations around the wellbore. FIG. 1(c) illustrates an open-hole gravel pack wherein the wellbore has no casing and the gravel pack material 3 is deposited around the wellbore sand screen 1.
A variation of a gravel pack involves pumping the gravel slurry at pressures high enough so as to exceed the formation fracture pressure (frac pack). FIG. 1(d) is an example of a Frac-Pack. The well screen 1 is surrounded by a gravel pack 3, which is contained by a wellbore casing 5 and cement 8. Perforations 6 in the wellbore casing allow gravel to be distributed outside the wellbore to the desired interval. The number and placement of perforations are chosen to facilitate effective distribution of the gravel packing outside the wellbore casing to the interval that is being treated with the gravel-slurry.
Flow impairment during production from subterranean formations can result in a reduction in well productivity or complete cessation of well production. This loss of functionality may occur for a number of reasons, including but not limited to, migration of fines, shales, or formation sands, inflow or coning of unwanted fluids (such as, water or gas, formation of inorganic or organic scales, creation of emulsions or sludges), accumulation of drilling debris (such as, mud additives and filter cake), mechanical damage in sand control screen, incomplete gravel pack, and mechanical failure due to borehole collapse, reservoir compaction/subsidence, or other geomechanical movements.
U.S. Pat. No. 6,622,794 discloses a screen equipped with flow control device comprising helical channels. The fluid flow through screen could be reduced via helical paths, fully opened, or completely closed by controlling downhole apertures from the surface. U.S. Pat. No. 6,619,397 discloses a tool for zone isolation and flow control in horizontal wells. The tool is composed of blank base pipes, screens with closeable ports on the base pipe, and conventional screens positioned in an alternating manner. The closeable ports allow complete gravel pack over the blank base pipe section, flow shutoff for zone isolation, and selective flow control. U.S. Pat. No. 5,896,928 discloses a flow control device placed downhole with or without a screen. The device has a labyrinth which provides a tortuous flow path or helical restriction. The level of restriction in each labyrinth is controlled by a sliding sleeve so that flow from each perforated zone (for example, water zone, oil zone) can be adjusted. U.S. Pat. No. 5,642,781 discloses a wellbore screen jacket composed of overlapped helical-shaped members wherein the openings allow fluid flow through alternate contraction, expansion and provide fluid flow direction change in the wellbore (or multi-passage). Such design may mitigate solids plugging of screen jacket openings by establishing both filtering and fluid flow momentum advantages.
Current industry well designs include little, if any, redundancy in the event of problems or failures resulting in flow impairment. In many instances, the ability of a well to produce at or near its design capacity is sustained by only a “single” barrier to the impairment mechanism (for example, screen for ensuring sand control in unconsolidated formations). In many instances the utility of the well may be compromised by impairment occurring in a single barrier. Therefore, overall system reliability is very low. Flow impairment in wells frequently leads to expensive replacement drilling or workover operations.
The current industry standard practice utilizes some type of sand screen either alone or in conjunction with artificially placed gravel packs (sand or proppant) to retain formation sand. All of the prior art completion types are “single barrier” completions, with the sand screen being the last “line of defense” in preventing sand from migrating from the wellbore into the production tubing. Any damage to the installed gravel pack or screen will result in failure of the sand control completion and subsequent production of formation sand. Likewise, plugging of any portion of the sand control completion (caused by fines migration, scale formation, etc.) will result in partial or complete loss of well productivity.
Lack of any redundancy in the event of mechanical damage or production impairment results in the loss of well productivity from single barrier completion designs. Accordingly, there is a need for a well completion apparatus and method to provide multiple flow pathways inside the wellbore that provides redundant flow pathways in the event of mechanical damage or production impairment.